Atomizer and method for atomizing

Abstract: Atomizer comprising a liquid inlet (14), a gas inlet (12) arranged to receive a pressurized flow of gas, a liquid flowpath extending from the liquid inlet (14) to a liquid stream outlet, and a curved gas flowpath extending from the gas inlet to a location adjacent the liquid stream outlet and including a supersonic flow region adjacent the liquid stream outlet, whereby supersonic gas flow adjacent the liquid stream outlet produces a shock wave which impinges on a liquid stream passing out through the liquid stream outlet for atomizing the liquid stream.

Description: The invention relates to an atomizer according to the preamble of claim 1 and to a method for atomizing according to the preamble of claim 6. There are known in the art a great variety of atomizers. The following documents are considered to be representative of the most relevant prior art: US-A-3 908 903; US-A-3 980 233; US-A-4 241 877; US-A-4 335 677; US-A-4 341 530; US-A-4 406 404; US-A-4 595 143; US-A-4 773 596; US-A-4 834 343; US-A-4 943 704; US-A-4 946 101; US-A-5 044 559; US-A-5 059 357; US-A-5 181 661 and GB-A-894 776. US-A-4 341 530 describes a slurry atomizer wherein a pressurized helical flow of steam proceeds about a longitudinal axis, along which a liquid channel is defined. Impingement of the helical flow of stream on the liquid channel draws liquid through the channel and causes breakup of the resulting axial liquid flow into droplets. US-A-4 241 877, on which the preambles of claims 1 and 6 are based, describes an atomizer comprising a liquid inlet; a gas inlet arranged to receive a pressurized flow of gas; a liquid flowpath extending from the liquid inlet to a liquid stream outlet; a gas flowpath extending from the gas inlet to an atomizer outlet and including a supersonic gas flow region; whereby supersonic gas flow produces a shock wave for atomizing the liquid stream in an atomizing flowpath region. Furthermore, US-A-4 241 877 discloses a method for atomizing comprising the steps of providing a pressurized flow of gas to a gas inlet and through a gas flowpath; providing a liquid flowpath extending from a liquid inlet to a liquid stream outlet; and causing the pressurized flow of gas to undergo supersonic flow at a supersonic gas flow region thereby to produce a shock wave for atomizing the liquid stream in an atomizing flowpath region. Finally, GB-A-894 776 describes an apparatus for producing a liquid spray by the interaction of a gas with the liquid. The gas enters the apparatus at a transverse direction to the liquid flow and flows along a helical pathway which produces a swirl in the gas flow. The swirling gas flow interacts with the liquid stream and breaks up the liquid into a spray. The gas, flowing at supersonic speeds, and liquid spray exit the apparatus at an outlet nozzle of the apparatus. The present invention seeks to provide an improved atomizer and an improved method for atomizing. These objects are achieved by the features defined in claims 1 and 6, respectively. Preferably, the generally helical flowpath extends about the liquid flowpath, which preferably is axial. In accordance with a preferred embodiment of the atomizer according to the invention, the generally helical flowpath includes a truncated conical subsonic flow region upstream of and adjacent to the supersonic gas flow region. In accordance with a preferred embodiment of the method according to the invention, the gas passes through a truncated conical subsonic flow region upstream of and adjacent to the supersonic gas flow region. In accordance with a preferred embodiment of the method according to the invention, the flow of the liquid stream is produced by suction resulting from the flow of gas. Other preferred developments of the invention are defined by the dependent claims. The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Fig. 1 is a pictorial illustration of atomizer apparatus constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a sectional illustration taken along the lines II - II in Fig. 1; Fig. 3 is an exploded view sectional illustration of the apparatus of Fig. 2; Fig. 4 is an enlarged illustration of part of the apparatus of Figs. 2 and 3; and Fig. 5 is a further enlarged illustration of part of the apparatus of Figs. 2 and 3. Reference is now made to Figs. 1 - 5 which illustrate atomizing apparatus constructed and operative in accordance with a preferred embodiment of the present invention. The atomizing apparatus of the invention preferably comprises a housing 10 defining a pressurized gas inlet opening 12 and a liquid inlet opening 14. Pressurized gas inlet opening 12 is preferably threaded so as to sealingly accept a suitably threaded pressurized gas nipple assembly 16, through which pressurized gas, such as air under a pressure in the range of 5.40 - 6.38 bar (5.5 - 6.5 atmospheres), is supplied to the housing 10. Alternatively a different inlet arrangement may be provided. Liquid inlet opening 14 preferably communicates with a multiple stepped axial bore 18 which communicates with pressurized gas inlet opening 12. Multiple stepped axial bore 18 includes a threaded portion 20, adjacent inlet 14, followed by a narrowed intermediate portion 22. Portion 22 is followed by a further narrowed intermediate portion 24, which communicates with inlet 12. Intermediate portion 24 is followed by a tapered down portion 26, which, in turn, is followed by a yet further narrowed portion 28. Portion 28 is followed by another tapered portion 30, which is followed by an elongate outlet portion 32. A liquid inlet pathway defining member 34 is threadably engaged in bore 18 and includes an inlet portion 38, which is located adjacent inlet 14. Member 34 also includes a threaded portion 40, which engages threaded bore portion 20, followed by a narrowed intermediate portion 42, which is formed with a recess 44 which accommodates a sealing ring 46. Portion 42 is followed by a further narrowed intermediate portion 48, which is followed by a grooved helical gas pathway defining portion 50, communicating with gas inlet 12. Portion 50 is followed by a slightly tapered portion 52, which terminates in a sharply tapered end portion 54. It can be seen particularly from a consideration of Fig. 5, that the sharply tapered end portion 54 of member 34 lies adjacent tapered bore portion 30 and elongate outlet bore portion 32. The junction of the tapered bore portion 30 and of the outlet bore portion 32 defines the boundary between subsonic gas flow region 64 and supersonic gas flow region 66. Liquid flows through a successively narrowing bore 58 in member 34 from a threaded liquid inlet 60 which receives a liquid inlet nipple assembly 62 to an outlet adjacent end portion 54 and elongate outlet bore portion 32. The tangential component of the gas flow adjacent the liquid flow, draws the liquid flow through bore 58 from a liquid supply which may be unpressurized. Shock waves generated by supersonic flow of gas in the region 66 between end portion 54 of member 34 and elongate outlet bore portion 32 of housing 10 impinge obliquely on the liquid flow and produce atomization thereof. It is a feature of the invention that the substantial tangential gas flow creates a significant vacuum drawing the liquid into supersonic atomizing engagement therewith. The relatively high vacuum which is realized using the present invention is believed to significantly enhance its atomizing efficiency, inter alia due to a high level of evaporation resulting therefrom. In practice, the following results have been obtained using the apparatus described above and illustrated in Figs. 1 - 5: Gas flow rate: 50 - 60 liter/min (1.76 cfm - 2.12 cfm) Gas inlet pressure: 6 bar Liquid flow rate: 5.5 - 6 liter/ hour Output liquid drop size (mean): 2 - 10 microns Vacuum level: 588.6 - 686.7 mbar (6 - 7 m water WG) Evaporation: approximately 10% of the water. It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow:

Claims: An atomizer comprising: a liquid inlet (60); a gas inlet (12) arranged to receive a pressurized flow of gas; a liquid flowpath extending from the liquid inlet (60) to a liquid stream outlet; a gas flowpath extending from the gas inlet (12) to an atomizer outlet (32) and including a supersonic gas flow region; whereby supersonic gas flow produces a shock wave for atomizing the liquid stream in an atomizing flowpath region; characterized in that said gas flowpath includes a generally helical gas flowpath (50) extending from the gas inlet (12) to a location adjacent the liquid stream outlet and includes said supersonic gas flow region (66) adjacent the liquid stream outlet, and said atomizing flowpath region comprises an elongate, generally cylindrical, bore portion (32) downstream of the supersonic flow region and extending to said atomizer outlet, whereby supersonic gas flow adjacent the liquid stream outlet produces in said region (66) adjacent the liquid stream outlet and in said elongate bore portion (32) said shock waves which impinge obliquely on a liquid stream passing out through the liquid stream outlet for atomizing the liquid stream. Apparatus according to claim 1, characterized in that the generally helical gas flowpath (50) extends about the liquid flowpath. Apparatus according to claim 1 or 2, characterized in that said liquid flowpath is axial. Apparatus according to claim 1, 2 or 3, characterized in that said generally helical gas flowpath (50) includes a truncated conical subsonic flow region upstream of and adjacent to the supersonic gas flow region. Apparatus according to any one of claims 1 to 4, characterized in that said liquid stream is drawn along said liquid flowpath from said liquid inlet (60) to said liquid stream outlet by a vacuum produced by said pressurized flow of gas tangential to said liquid. A method for atomizing comprising the steps of: providing a pressurized flow of gas to a gas inlet (12) and through a gas flowpath; providing a liquid flowpath extending from a liquid inlet (60) to a liquid stream outlet; causing the pressurized flow of gas to undergo supersonic flow at a supersonic gas flow region thereby to produce a shock wave for atomizing the liquid stream in an atomizing flowpath region; characterized by: providing said pressurized flow of gas through a generally helical gas flowpath (50); and causing said supersonic gas flow region (66) to be located adjacent said liquid stream outlet thereby to produce in said region (66) adjacent the liquid stream outlet and in an elongate, generally cylindrical, bore portion (32) downstream of the supersonic flow region and extending to said atomizer outlet said shock waves which impinge obliquely on said liquid stream for atomizing the liquid stream. A method according to claim 6, characterized in that said liquid flowpath is axial and said generally helical gas flowpath (50) extends about the liquid flowpath. A method according to claim 6 or 7, characterized in that the flow of the liquid stream is produced by suction resulting from the flow of gas. A method according to claim 6, 7 or 8, characterized in that the gas is passed through a truncated conical subsonic flow region upstream of and adjacent to the supersonic gas flow region. The method according to any one of claims 6 to 9, characterized in that said liquid stream is drawn along said liquid flowpath from said liquid inlet (60) to said liquid stream outlet by a vacuum produced by said pressurized gas flow tangential to said liquid.

Inventors: TAVOR ELHANAN, TAVOR, ELHANAN
Applicants: TAVOR ELHANAN, TAVOR, ELHANAN
Application year: 1994
Main classification: B05B7
IPC codes: B05B7, B05B17, B05D1